The primary goal of the proposed research is to study age-related changes in attentional processes. The main motivation behind this research project is that a better understanding of aging is of increasing importance due to the growing proportion of older individuals in the society. Objective and scientific information on the effects of aging on performance is critically needed so that judicious economic, effects of aging on performance is critically needed so that judicious economic, social, and retirement policy can be made. Attention is proposed here to be a prime agent through which aging effects on performance are manifest. More specifically, research is proposed to study the effects of aging on pilot time-sharing performance. Pilot performance represents a complex performance that may be particularly prone to the adverse effects of aging and attentional limits. The research focuses on time-sharing performance because it has been identified as a critical element of pilot performance. Pilots are considered to have an expertise in time-sharing activities that could not have developed during a typical laboratory study. comparing pilot's with non-pilot's performance thus allows an examination of the interactive effects of age and expertise. Another reason for studying pilot performance is prompted by the controversy associated with the federal regulation that prohibits a commercial pilot who has reached age 60 to be the pilot-in-command or co-pilot. This controversy begs a better understanding of the effects of aging on pilot performance. A secondary goal of the proposed research is thus to attain a better understanding of the relationship between aging and pilot performance. In particular, three hypotheses are tested in the proposed research: (a) older adults ar subject to the same structural constraints in time-sharing performance as are younger adults, (b) structural constraints in time- sharing performance are not easily eliminated by practice, and (c) age- related performance decrement is due to reduced processing resources. These hypotheses will be tested within the framework of Wickens' multiple resource model. A test battery with tasks that have previously been shown to be flight relevant or age-dependent will be developed. These tasks will be performed alone or time-shared with another task. Navon's optimum- maximum method of inducing resource allocation will be used. The causal relationship among age, attention, expertise, and time-sharing performance will also be explored via a path analysis. Pilots as well as non-pilots between the age 20 and 69 will be tested.